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Orthopedic implants provide patients with an opportunity to regain functionality lost from illness, disease, or injury. Recent advancements in additive manufacturing (AM) techniques have allowed for the increased customization of Ti‐6Al‐4V ELI (extra low interstitials) implants to complement natural variations in the human anatomy. Yet, the low bioactivity of Ti‐6Al‐4 V ELI and possible adverse effects from the leeching of aluminum and vanadium complicate the post‐operation recovery process. In this work, Ti‐6Al‐4 V ELI samples are printed using the electron beam melt technique in two directions and coated with diamond‐like carbon (DLC) to examine whether their biological properties can be improved. By conducting in vitro studies with Saos‐2 osteosarcoma cells, the effects of morphology and surface chemistry are correlated to the bioactivities of the coated and uncoated samples. The outcome of the study suggested that DLC coating is a viable method for controlling the surface bioactivity of a material. It indicates that a carbon coating, along with an appropriate topography, has the potential to promote the proliferation and maturity of bone cells and hence enhance the performance of additively manufactured products in next‐generation biomedical applications. [ABSTRACT FROM AUTHOR]

The tribological properties of TiN-based coatings can be substantially influenced by the choice of substrate bias employed during physical vapor deposition. However, the effects of applied substrate bias voltages during cathodic arc evaporation on to the scratch adhesion strength and wear resistance of TiNiN coatings have not been previously studied. In this present work, a series of TiNiN coatings were fabricated onto tool steel (M2) substrates using the cathodic arc evaporation method by applying a range of bias voltages to the substrate. The aim of this study is to investigate the scratch response and wear performance of these coatings along with an investigation of the deformation mechanisms in operation during scratch and wear tests. The best scratch adhesion strength (i.e., greater L C1 , L C2 and CPRs values) was noted for the coating prepared at a bias voltage of −100 V, which was ascribed to the synergistic responses arising from superior mechanical properties, the influence of a high compressive residual stress and a fine, equiaxed nanocomposite structure, that acted to promote effective resistance against cohesive and adhesive failure. Further, the failure mechanisms under progressive loading conditions were also investigated through observation of the complex crack patterns generated, compressive residual stress values and the coatings' hierarchical design. An approximately 85 % enhancement in wear resistance for these TiNiN coatings was achieved as the bias voltage was increased from 0 V to −100 V. This −100 V coating exhibited the highest values of H/E r (>0.1) and W e (>60 %), as well as the highest Ni concentration (~ 4 at.%). • TiNiN films were prepared by cathodic arc evaporation over a range of bias voltages. • A ~41 % increase in L C1 value was noted as the bias increased from 0 to −100 V. • Improved scratch properties are related to the higher H/E r and H3/E r 2 ratios. • An adhesive TiNi layer acted to impede propagation of cracks into the substrate. • A ~85 % reduction in wear rate was achieved at −100 V relative to 0 V. • The wear mechanism of the coatings is governed by the third-body tribo-products. [ABSTRACT FROM AUTHOR]

Fig. Plan view SEM images of the surface of the TiNiN coatings deposited at substrate bias values of (a) 0 V and (b) −100 V with their corresponding XTEM bright-field images (c and d). These images reveal that at the higher substrate bias there is a significant reduction in the density of macroparticles together with structural densification. Significantly higher values of hardness and Young's modulus are achieved at the high bias voltage. [Display omitted] • A hardness of 34.2 GPa was attained in the TiNiN coating prepared at −100 V. • Structural densification was noted at higher bias voltages (from −50 to −100 V). • Macroparticles induced during deposition are primarily comprised of α-Ti grains. • A reduction in macroparticle density was achieved at ≥ -100 V. The application of a negative substrate bias during physical vapor deposition can have important effects on the surface morphology, structure and properties of ceramic-based coatings. In this study, a number of TiNiN coatings were prepared onto AISI M2 steel substrates via cathodic arc deposition method by employing a range of different negative substrate bias voltages. The objective of this work is to study the influence of bias voltage on the surface morphology, microstructure and mechanical characteristics of these thin films. A change from a fine columnar grained structure to highly refined equiaxed grains was noted with increasing bias from 0 to −50 V, associated with the energetic ion bombardment at the higher substrate bias. A very high hardness value of ∼ 34.2 GPa was attained at a −100 V substrate bias, which was attributed to the synergistic effects of a number of factors such as the presence of compressive residual stresses, solid solution hardening effects along with grain refinement. In addition, significant reduction in the density of microparticle-related defects generated in these coatings was achieved at ≥ -100 V, which can presumably be ascribed to the higher repulsive force induced at higher substrate bias values. [ABSTRACT FROM AUTHOR]

Tantalum coatings have wide applications including as corrosion resistant coatings and radiopaque films for biomedical implants. However, producing coatings of sufficient thickness with the desired mechanical properties remains a substantial challenge. In this study, we show that the microstructure and properties of thick Ta films deposited on NiTi wires can be controlled significantly by pre-treating the substrate surface via ultrasonication followed by Aqua Regia etchant, or by plasma-based etching alone, while maintaining overall adhesive strength. Films from plasma and chemically etched samples exhibited substantially greater bulk texturing in the <111> direction than the control film, also yielding more elongated and columnar grains. The extent of <111> texturing in each sample was reflected in differences in Σ3 CSL boundary density. Additionally, only plasma etching yielded a β-Ta secondary phase. These microstructural observations demonstrate that film phase composition, texturing, grain shape distribution and grain boundary characteristics can be optimised for particular applications, simply by applying different NiTi substrate pretreatment regimes. It is suggested that this bears significant implications for influencing bulk properties such as cohesive and shear strength, as well as ductility, conductivity and cohesion in thick tantalum coatings. • Bulk <111> texturing in Tantalum coatings with etched substrates • Plasma etching introduces ß-Ta into the majority α-Ta film matrix. • Σ3 CSL boundary density substantially regulated by pretreatment method • More uniform and columnar grains in Ta film under chemical etching • Different film microstructures produced with similar adhesive strength [ABSTRACT FROM AUTHOR]

The bioactivity of magnetron sputtered thin film metallic glasses (TFMGs) of Zr 48 Cu 36 Al 8 Ag 8 (at.%) on titanium substrates was tested for bio implant applications. The structural and elemental compositions of TFMGs were analyzed by XRD, XPS and EDAX. X-ray diffraction analysis displayed a broad hump around the incident angle of 30–50°, suggesting that the coatings possess a glassy structure. An in situ crystal growth of hydroxyapatite was observed by soaking the sputtered specimen in simulated body fluid (SBF). The nucleation and growth of a calcium phosphate (Ca–P) bone-like hydroxyapatite on Zr 48 Cu 36 Al 8 Ag 8 (at.%) TFMG from SBF was investigated by using XRD, AFM and SEM. The presence of calcium and phosphorus elements was confirmed by EDAX and XPS. In vitro electrochemical corrosion studies indicated that the Zr-based TFMG coating sustain in the stimulated body-fluid (SBF), exhibiting superior corrosion resistance with a lower corrosion penetration rate and electrochemical stability than the bare crystalline titanium substrate. [ABSTRACT FROM AUTHOR]

Abstract: Coatings on implants are aimed to achieve some or all of the improvements in abrasion, corrosion resistance, metal ion release protection, increased bioactivity, biocompatibility, and ultimately an improved environment and structure for new bone attachment. Adhesion, mechanical properties and testing methods are used to determine the viability of coated implants or devices and their performance under simulated physiological environments. Perforation or delamination of the coatings can expose the substrate to accelerated wear or corrosion, and the released coating particles may act to accelerate third party wear resulting in a negative host response. An in-depth understanding of the adhesion of the implants and the susceptibility of the coating to cracking and delamination are critical important reliability issues. The aim of this review is to give a brief description on the various techniques used to produce micro and nanocoatings currently used or being investigated within the biomedical field. This is followed by an overview of some of the most widely used test methods for measuring mechanical properties and adhesion performance of coatings used in medical applications. [Copyright &y& Elsevier]

The microstructures of nanostructured Ti–Si–N hard coatings were investigated by transmission electron microscopy and pulsed laser atom probe. C and O impurities were detected. No evidence of increased Si levels at the grain boundaries was found, suggesting that Si is either in the form of a layer too thin to be detected using the techniques employed or in the form of a solid solution of SiN clusters. [Copyright &y& Elsevier]

Abstract: The effect of substrate and surface roughness on the contact fracture of diamond-like carbon coatings on brittle soda-lime glass substrates has been investigated. The average surface roughness (R a) of the examined samples ranged from 15nm to 571nm. Contact damage was simulated by means of spherical nanoindentation, and fracture was subsequently assessed by focused ion beam microscopy. It was found that, in the absence of sub-surface damage in the substrate, fracture occurs in the coating in the form of radial, and ring/cone cracks during loading, and lateral cracks during unloading. Increasing the surface roughness results in a decrease in the critical load for crack initiation during loading, and in the suppression of fracture modes during unloading from high loads. When sub-surface damage (lateral cracks) is present in the substrate, severe spalling takes place during loading, causing a large discontinuity in the load–displacement curve. The results have implications concerning the design of damage-tolerant coated systems consisting of a brittle film on a brittle substrate. [Copyright &y& Elsevier]